The overall objective is to understand how specific genes are "turned-on" during cellular development. We have concentrated predominantly on the E. coli bacteriophage lambda as the model system for study because of its amenability to the refined biological and biochemical techniques now available. In vivo RNA transcripts of bacteriophage lambda are being mapped precisely on the genome with particular emphasis on the determination of their exact transcriptional start-points. These data will allow us to differentiate between two possible models ("anti-termination" or "new initiation") as mechanisms for "turn-on" of messenger RNA at the transcriptional level. The stability of a particularily hyperlabile RNA transcript of bacteriophage lambda is being investigated in bacterial mutants with presumed enzyme defects in RNA metabolism. Such mutants may be of potential value in providing the mRNA stabilization necessary for the detailed characterization of in vivo RNA transcripts. Furthermore, these studies may help us understand the mechanisms and enzymology of RNA processing and degradation.